1. Field of the Invention
The present invention relates to a heater including a laminated sheet heater and a temperature detecting device, and to a battery structure with this heater with temperature detecting device.
2. Description of Related Art
For fixing a temperature detecting device (a temperature sensor or the like) to the surface of a heater to detect the temperature of the heater, adhesive agents, adhesive tapes, or the like are often used as a fixing means.
Jpn. unexamined patent publication No. 2004-356087 discloses a heater having a substrate, a heating element placed on the substrate, and a fixing material placed over the substrate in such a manner as to cover the heating element. This publication discloses in the first embodiment the heater that includes a temperature detecting device embedded therein with a fixing material as well as the heating element.
Thinner heaters have been desired in recent years, increasing demands for a laminated sheet heater configured such that a heating element made of metal foil in a predetermined pattern is sandwiched between two insulating resin films (polyimide film or the like) (see Jpn. unexamined patent publication No. 2004-355882).
This laminated sheet heater has been used for example in heating a battery in cold environments to enhance output characteristics of the battery. To be concrete, there has been proposed a technique that a laminated sheet heater is placed inside a bottom of a battery for vehicle to heat the battery using a household power source (see Jpn. unexamined utility model publication No. 60(1985)-192367).
To this laminated sheet heater, there is also a demand to attach a temperature detecting device capable of detecting the temperature of the heater. However, this heater is very small in thickness and could not internally hold the temperature detecting device as in the above publication '087.
The technique of fixing the temperature detecting device with adhesive agents or adhesive tapes is apt to be influenced by degradation of adhesive power caused by heat of the heater and aged deterioration of the adhesive agent. This may cause a problem that a temperature measuring portion of the temperature detecting device could not be held stably in fixedly contact with the heater. Thus, the temperature of the heater could not be measured accurately in the long term.
Under the above circumstances, the inventors of the present invention have come up with a configuration that the temperature detecting device is placed in contact with the surface of the laminated sheet heater and fixed thereto with use of a mechanical fastening device such as a metal fixing member (a rivet or the like). However, when the temperature detecting device is fixed to the laminated heater including two insulating resin films with use of the mechanical fastening device, the two insulating resin films are likely to be deformed or distorted by the fastening power of the mechanical fastening device. This may cause the surface of the laminated heater that makes contact with the temperature detecting device to be deformed or distorted, thus generating a gap between the temperature measuring portion of the temperature detecting device and the surface of the laminated heater. Accordingly, the temperature detecting device may not accurately detect the temperature of the laminated heater.
Furthermore, after fastening, creep of the insulation resin film (i.e., a phenomenon in which deformation or distortion gradually increases over time) may affect a fastened portion, gradually decreasing the thickness of the fastened portion of the insulation resin film. As a result, the fastening power will progressively go down, so that a gap is likely to be formed between the temperature measuring portion of the temperature detecting device and the surface of the laminated heater. Consequently, the temperature detecting device may not detect the temperature of the laminated heater accurately in the long term.